The problems of sealing the moving parts of an energy-producing device are well known. Indeed the problems of sealing a piston and cylinder combination have been so severe in the past that the problem has led to the development of alternative devices for extracting energy, these alternative devices then having a different type of sealing apparatus as for example of the centrifugal type or other type to avoid the problems of pressure sealing a sliding motion of a piston within a cylinder. The standard method for sealing a cylinder and piston combination is with oil rings which are discontinuous rings of metal located in the piston wall that slideably engage the interior surface of the cylinder. The quantity and tolerances of construction of these oil rings produces a reasonably leak-tight piston-to-cylinder combination for many general purposes and this device combination is well-known in automobile engines, air compressors and other piston driven apparatus. However, despite the presence of a tortuous or labyrinthine type of path, leakage in fact does occur. The problem is that this leakage reduces power, because at peak pressure some of the driving gas is bled off past the seals. Additionally, abrasive contaminants and pollutants may pass the seals and cause abrasion at the seals and of the cylinder wall. Such contaminating materials may also contaminate the oil in the crank case area below the pistons, leading to abrasion of other moving parts. The production and presence of pollutants and abrasives severely decreases the life of the seals of a cylinder and the piston combination. Additionally, the friction of a plurality of oil rings against the cylinder wall tends to reduce the power available.
The problems of pollutants, leakage and abrasives are even more aggravated when higher temperature conditions are attempted within the piston-cylinder combination. Most seals of the elastomeric type have maximum temperature rating in the 500.degree.-600.degree. F. (260.degree.-315.degree. C.) range although some modern seals actually have temperature ratings as high as 900.degree. F. (482.degree. C.). Both of these problems, temperature and pollution abrasion are discussed in U.S. Pat. No. 4,120,161 to Gedeit when he states that he strives to keep the operating temperatures to a maximum of 800.degree. F. (425.degree. C.) and also attempts to segregate combustion gases, which also contain pollutants and abrasives, away from the piston and cylinder power generating train, to protect the pistons and lubricating oils from the carbon deposits, corroding chemical residue and abrasive grit that would be leaking past any seals. In addition to reducing the life of the seals, pistons and cylinders, there are the maintenance considerations and "down-time" requirements simply to replace worn or deteriorating seals on a periodic basis. Such a maintenance time period becoming shorter and shorter or occurring more often as the temperatures increase.
The entire situation is aggravated because engine efficiency is known to be at its greatest when the engine operating temperatures are at the highest possible levels. The Carnot engine is the theoretical embodiment of the perfect heat engine. The Carnot cycle comprises a four-step cycle beginning with an isothermic expansion followed by an adiabatic expansion, these in turn being followed in order by an isothermic compression and an adiabatic compression. If all of these steps are done in a thermodynamically reversible way, the result is a rectangular plot on a temperature-entropy diagram which is known as a standard way of expressing such a thermodynamic cycle. Most attempts to produce a more efficient engine have centered upon attempts to approximate a Carnot type of cycle. Carnot efficiency is expressed as the difference in the enthalpies represented by the two adiabatic portions of the cycle divided by the enthalpy of the fluid during its adiabatic expansion. In the thermodynamically reversible Carnot cycle this can be further simplified to be the difference between the temperature of the working fluid in the engine and the temperature of the heat sink divided by the temperature of the working fluid in the engine. Therefore it can be seen that the greater the difference between the heat sink temperature and the cylinder operating temperature, the higher the efficiency of the engine. Heretofore, efficiencies based upon increasing the temperature at which the cylinder operates have been limited by the maximum temperatures not of the metals but of the sealing materials. As the temperature increased the efficiency losses due to loss of compression by leakage past deteriorating or inherently leaking seals was the limiting factor.
Therefore, there is a need for an apparatus for sealing a high temperature engine piston and cylinder combination using conventional and readily obtainable seal materials. There is also a need to improve the design of pistion and cylinder combinations to allow the use of conventional and readily obtainable materials to be used in the construction.